I'm not a teacher (might be able to deal with 30 kids for...10 minutes tops
), but love the idea of having classroom themes. I only really ever had one (elementary). It was the rainforest. We learned about it throughout the year and then the room got decorated to resemble one (tubing from floor to ceiling resembling tree trunks and green construction paper loops connected together, we made them, as the greenery coming off the trunks). Then there was some sort of play for the parents.